Bruson U.S. Pat. 2,414,089, January 14, 1947, discloses the preparation of esters of hydroxydicyclopentadiene with unsaturated monocarboxylic acids including acrylic acid (Ex. 9), methacrylic acid (Ex. 8), and numerous other unsaturated acids mentioned in the passage of column 3, line 67 to column 4, line 24. Use of the esters as vehicles for paints, varnishes and similar coating materials is mentioned in column 4, lines 25 to 27, and in the passage of lines 62 to 75 of column 6, the linoleate (of Ex. 3) is used with a drier to form a film that is baked to form a varnish-like coating, and other unsaturated higher fatty acids are suggested for this use. The passage in lines 49 to 53 of column 4 states that the new esters may be mixed with drying oils, alkyd resins, hydrocarbons, such as rubber or cyclized rubber, and other oils and resins.
P. D. Bartlett and Abraham Schneider, J.A.C.S. 68, 6 (1946) give the correct structure of the esters produced by Bruson, which he had erroneously named as a result of his theory as to rearrangement.
Hoover U.S. Pat. No. 2,462,400, February 22, 1949, discloses the preparation of copolymers of 20 to 50% by weight of dihydrodicyclopentadienyl methacrylate with saturated (C.sub.8 -C.sub.18) aliphatic monohydric alcohol esters of methacrylate acid using an organic peroxide initiator. A solution of the copolymer containing a drier is then used for coating substrates, the coating being air-dried.
In U.S. Pat. No. 3,743,615, a vinyl monomer, such as an alkyl acrylate or methacrylate, styrene, or the like is added to fast air-drying oil-modified alkyd resins.
Dicyclopentenyl acrylate or methacrylate has been suggested for use in photosensitized coating compositions which are to be polymerized by radiation. See U.S. Pat. Nos. 3,650,669 and 3,772,062. However, such compositions require a photo-initiator system, the products are frequently lacking in durability and require the use of high-intensity UV light sources in close proximity to the coated articles to obtain the extent of curing desired or needed in a practical time for industrial operation.
Commercially available coating compositions of autoxidizable type, including impregnating versions thereof, based on oil-modified polyesters or alkyd resins in which the oil modification comprises at least one unsaturated oil of semi-drying or drying type generally provide coating or impregnating films which are often of limited hardness and are seriously lacking in other properties, being especially susceptible to deterioration (yellowing, discoloration, cracking, shrinking and other distortions; decomposition, removal, and the like) by wear and abrasion, chemical attack, particularly organic solvents and alkaline materials, weathering forces, such as wind, rain, and radiation including ultraviolet light rays of the sun, other natural radiation including cosmic rays, e.g., x-rays, B-rays, gamma-rays, as well as radiation emitted by all sorts of artificial means, as in lasers, x-ray machines, and radioactive materials (artificial as well as natural). Coating compositions used to make fluorescent screens in oscilloscopes, television picture tubes, and electron microscopes, are examples of compositions subject to radiation attack.
The present invention is concerned with novel air-drying coating compositions based on alkyd resins having at least one unsaturated component and especially those modified by a drying or semi-drying oil. The new coating compositions comprise dicyclopentenyl acrylate or methacrylate; this monomeric component may consist of either the acrylate or methacrylate or mixtures of both; either of them and mixtures of them are hereinafter referred to generically as DCP(M)A, the individual acrylate and methacrylate being simply referred to as DCPA and DCPMA respectively.
The reactive DCP(M)A monomer or monomers with which the present invention is concerned is the dicyclopentenyl acrylate or methacrylate, alternatively called dihydrodicyclopentadienyl acrylate or methacrylate respectively. This ester may be obtained by the addition of acrylic acid or methacrylic acid respectively to one of the double bonds of dicyclopentadiene. This hydrocarbon compound is represented by the formula: ##STR1## and has the name: 3a,4,7,7a-tetrahydro-4,7-methanoindene (Ring Index, Patterson, 2nd Edition, page 293).
The acrylic ester of the dicyclopentadiene is believed to have the following formula: ##STR2## wherein R is H or CH.sub.3. The (meth)acryloxy substituent may be on either the 5 or 6 position, the commercial product being a mixture of the two isomers.
Using the numbering system of Formula I hereinabove for the compound of Formula II, it can be seen that the dicyclopentenyl acrylate or methacrylate represented therein may also be called 3a,4,5,6,7,7a-hexahydro-4,7-methanoindenyl acrylate-5 (or 6) or methacrylate-5 (or 6).
The DCP(M)A is a reactive high-boiling liquid acrylic ester monomer or monomer mixture which has been found to have an unusual combination of desirable characteristics for use in coatings: low viscosity, volatility, and toxicity; hydrophobicity and outstanding hydrolytic stability even under acid or alkaline conditions; an outstanding compatibility with a wide range of polymeric and/or resin-forming condensates so that it can be used with or without a small amount of another solvent to form a solution of a polyester having maleate-fumarate type of unsaturation and/or drying oil unsaturation, such as an oil-modified alkyd, optionally with another polymer and/or resin-forming condensate, which can be applied as a coating to any substrate; a reactivity with an unsaturated alkyd, especially with an oil-modified alkyd, optionally in conjunction with other non-volatile polymeric and/or resin-forming materials, in the presence of a metal-containing siccative or drier whereby the exposure of a coating containing the reactive monomer, the oil-modified alkyd, (optionally also another polymer and/or condensate), and a siccative, with or without other solid ingredients, e.g., pigments, fillers, plasticizers, dyes, etc. to normal atmospheric conditions results in the production of solid films having a desirable combination of characteristics. In the case of 100% solids compositions containing no solvent other than the non-volatile reactive monomer solvent, air-drying to solid state is accomplished without the necessity of volatilizing any solvent material, thereby reducing air pollution and wastage.
The incorporation of DCP(M)A (which acts as a non-volatile reactive diluent or solvent) as the entire vehicle in coating compositions comprising, dissolved in the vehicle, commercially available oil-modified alkyd resins, the polycarboxylic acid component of which is predominantly or primarily of aromatic type, e.g., o-phthalic acid or phthalic anhydride, has sometimes been found to yield products which are extremely hard, in fact, so hard as to be of limited specialty use, for instance, when more than 25% by weight of DCP(M)A is used in conjunction with less than 75% by weight of such an alkyd resin. Excessive hardness in these instances can be avoided if the DCP(M)A is used as a major component of the reactive vehicle in conjunction with a minor amount of another non-volatile reactive liquid ester of a higher (C.sub.10 -C.sub.20) aliphatic alcohol with acrylic acid or methacrylic acid, and latter reactive monomer being used in sufficient amount relative to the DCP(M)A to counter balance the excessive hardness in the film produced by the DCP(M)A. When it is desired to avoid the use, or to minimize the amount used of volatile non-reactive solvent in coating compositions, the reduction in viscosity of the compositions to a suitable level for application in any particular way (spraying, brushing, roll-coating, etc.) can thus be effected in most, if not all instances by adjusting the proportion of the non-volatile reactive component. Such component may consist of DCP(M)A when an alkyd is of Type A (as defined herein) or when up to about 25% by weight of DCP(M)A is used with about 75% or more alkyd of Type B (as defined herein). However, such component may consist of a mixture of a major amount of DCP(M)A and a minor amount of higher aliphatic alcohol esters of acrylic or methacrylic acid as mentioned above; in this instance, the alkyd may be of either Type A or Type B or a mixture thereof and the relative proportions between the non-volatile reactive component of the vehicle and the alkyd may be anywhere in the ranges specified hereinafter. It is to be understood that, in practice, a proportion of volatile, non-reactive diluent or solvent may be incorporated as a part of the vehicle in the coating composition to be applied in proportions stated hereinafter, but it is preferred in many instances to use such a solvent in small proportions, if at all.
The essential binder-forming components of the coating compositions of the present invention are:
a. Dicyclopentenyl acrylate (DCPA) or methacrylate (DCPMA) or a mixture thereof (Type A), or a mixture of DCP(M)A with at least one other non-volatile reactive monomer, e.g., a (C.sub.10 -C.sub.20) alkyl acrylate or methacrylate, (Type B), PA1 b. A polyester of alkyd having at least one unsaturated component selected from (1) maleic acid or anhydride or fumaric acid type residues or moieties and (2) drying or semidrying oil type residues or moieties, e.g. in linolenic acid. PA1 c. A siccative or mixture thereof. PA1 a. An essentially non-volatile reactive monomeric material consisting essentially of: PA1 b. A polyester or an alkyd having at least one unsaturated component selected from (1) maleic acid or anhydride or fumaric acid type residues or moieties and (2) drying or semi-drying oil type residues or moieties, preferably an oil-modified polyester (or alkyd) comprising: PA1 c. A polyvalent metal-containing drier or siccative, and if desired,: PA1 d. A polyethylenically unsaturated monomer of low volatility and having at least 2 groups of the formula H.sub.2 C=C&lt; up to 25% by weight, but preferably not over 2% by weight, based on total binder weight, to improve water-resistance, solvent-resistance, abrasion-resistance, blocking-resistance, and the like. Examples include glycol or polyol (meth)acrylates, e.g. ethylene glycol di(meth)acrylates, trimethylolpropane tri(meth)acrylate, neopentyl glycol di(meth)acrylate; 1,6-hexanediol di(meth)acrylate; pentaerythritol tri- and tetra- (meth)acrylate; 1,3- and 1,4-butanediol di(meth)acrylate; also allyl (meth)acrylate. PA1 e. A volatile stabilizer for inhibiting the oxidizing action of the drier, PA1 f. A volatile solvent in an amount of up to about 30% by weight, but preferably not over 20% by weight, of the entire weight of formulated coating composition ready for application, PA1 g. A pigment and/or filler, a dispersing agent therefor, and/or other materials conventionally used in paints, varnishes and the like coating compositions.
To this mixture of reactive monomer a) and alkyd b), at the time of use, there is added, if the mixture doesn't already contain a drier:
The relative proportions between the several essential components mentioned may be as follows. The amount of reactive monomer component a) including DCPA or DCPMA may range from about 15 to about 75% of the total amount of components a) and b). However, preferred compositions contain component a) in an amount of about 25 to 60% by weight of a) + b). The proportion of the drier may be quite low and is generally used in the amount of 0.0005 to 2% metal content by weight of a) + b). The drier may be added to the composition prior to storage provided such addition is made in the absence of oxygen or a volatile stabilizer inhibitor is included in the composition to prevent the oxidizing action of the drier and the composition is placed in closed storage containers to prevent volatilization of the inhibitor.
In accordance with one preferred embodiment of the present invention referred to hereinafter as Type A, it has been found that extremely useful oil-modified alkyd resin products can be obtained by the use of DCP(M)A as the predominating, even the entire, vehicle provided the oil-modified alkyd resin is based on polycarboxylic acid predominantly or exclusively of aliphatic dicarboxylic acid component(s) in which the dicarboxylic acid is a saturated or unsaturated aliphatic acid having at least four carbon atoms and up to 36 to 40 or more carbon atoms. The dibasic acids are preferably those in which carboxylic groups are separated by unsubstituted saturated or unsaturated aliphatic hydrocarbon groups although such groups may be substituted by hydroxyl groups as in malic acid or even halogen atoms, e.g. chlorine. Although phthalic acid or anhydride or other aromatic polyacid may form a part of the polycarboxylic acid component of the polyester, it is preferred that at least 30% by weight, and preferably at least 50% by weight of the polycarboxylic component used in making the polyester should be of the aliphatic type just defined. In the optimum situation when DCP(M)A constitutes essentially the entire component a), no aromatic component is present in either the polycarboxylic acid component or any other part of the oil-modified alkyd used in accordance with the present invention. Examples of the aliphatic dicarboxylic acids (useful in either acid or anhydride form) that may be used in forming the unsaturated alkyds including the oil-modified alkyds of the present invention include adipic, maleic, fumaric, pimelic, suberic, azelaic, and sebacic acid. Also useful are the various commercially available grades of dimer acid obtained by polymerizing linoleic acid as described in U.S. Pat. No. 2,482,761 and J. Am. Oil Chemists Association 24, 65 (1947). The composition of one such dimer acid (sold under the designation Emery 955 dimer acid) is described in H. F. Payne, "Organic Coating Technology," Vol. I, pp. 275-7, John Wiley & Sons, Inc., N.Y., 1954, and apparently contains a small proportion of trimers having three carboxyl groups. The pertinent disclosure of these three references is incorporated herein by reference.
In another preferred embodiment, hereinafter referred to as Type B, extremely useful compositions are also obtained from oil-modified alkyd resins derived from, or based on polycarboxylic acids of either aliphatic or predominantly or entirely aromatic types by using, as component a), the DCP(M)A in conjunction with a relatively non-volatile methacrylic or acrylic acid ester of a long-chain aliphatic alcohol, namely, an aliphatic alcohol having from 10 to 20 or more carbon atoms. Such aliphatic esters include decyl acrylate, isodecyl acrylate, undecyl acrylate, lauryl acrylate, cetyl acrylate, pentadecyl acrylate, hexadecyl acrylate and octadecyl acrylate, as well as the corresponding methacrylates and the unsaturated analogues such as oleyl acrylate or methacrylate, linoleyl (meth)acrylate, linolenyl (meth)acrylate, etc.
Instead of, or in addition to, the (C.sub.10 -C.sub.20) alkyl or (C.sub.10 -C.sub.20) alkenyl acrylates and methacrylates mentioned hereinabove, there may optionally be included other ethylenically unsaturated monomers of non-volatile character. Examples include vinyl stearate, vinyl laurate, vinyl oleate, and dialkyl fumarates, maleates, and itaconates where the alkyl groups include 1 to 20 carbon atoms. In this Type B preferred embodiment, the amount of such monomers may be from 10 to 40% by weight of the component a), the DCP(M)A being present in predominant amount (and making up the balance to 100%), namely 90% to 60%, of this reactive monomer component a).
Thus, the reactive monomer component may comprise besides the DCP(M)A up to 40% by weight of the long-chain aliphatic alcohol (meth)acrylate. This component of the composition may serve as the entire vehicle so that essentially no volatile solvent component is employed, thereby obtaining a composition that may be considered to be 100% solids in that all components serve to develop the solid resinous mass upon oxidation and polymerization resulting from the inclusion of a drier or siccative. Whereas the most advantageous compositions from the standpoint of control of pollution, minimization of the risks of flammability and toxicity to personnel employing the compositions are those of at least 70%, and preferably 80% to 100%, solids characteristic, nevertheless, the invention also contemplates compositions wherein an amount of volatile solvent may be employed in conjunction with the liquid monomeric component above described to facilitate adjustment of viscosity for application by brushing, spraying, or otherwise, the proportion of volatile solvent being not over about 30% by weight, and preferably not over 20% by weight, of the entire weight of the coating composition.
The coating compositions of the present invention thus may, in more specific aspect, comprise:
1. (In Type A compositions) dicyclopentenyl acrylate (DCPA) or methacrylate (DCPMA) or a mixture thereof, this component being generically indicated by the expression DCP(M)A, or PA2 2. (In Type B compositions) DCP(M)A in predominant proportion in admixture with up to 40% by weight, based on the weight of component a), of a non-volatile ethylenically unsaturated monomer, such as an aliphatic ester of acrylic acid or methacrylic acid in which the alcoholic moiety has from 10 to 20 carbon atoms and may be saturated or unsaturated, PA2 1. (In Type A compositions) An alkyd in which the dicarboxylic acid component is predominantly or exclusively an aliphatic dicarboxylic acid (or anhydride thereof) having a hydrocarbon group or chain of 2 to 40 or more carbon atoms separating the carboxyl groups and zero to 29% by weight of phthalic acid or anhydride, or PA2 2. (In Type B compositions) An alkyd as in (1) or an alkyd in which the dicarboxylic acid component may be predominantly or exclusively of aromatic character,
Besides the essential components mentioned hereinabove, there may also be included various addition or condensation polymers of thermoplastic type, to the extent that they are compatible with component a) in the presence of component b) with or without a small amount of organic solvent f). Instead of thermoplastic addition polymers, thermosetting condensates, such as an aminoplast, or phenoplast, may be included again to the extent they are compatible. Generally the amounts of such additional polymers and/or condensation products may be from about 1/2 to 25% by weight based on the weight of a) + b).
The binder of the compositions outlined above consists essentially of the components a) and b) (plus d) if included, and any addition and/or condensation polymers just mentioned in the preceding paragraph, if included) and the vehicle consists of these components and the solvent f) if included. Taking these components into consideration, the preferred relative proportions between them may be as follows: